Oscheius microvilli n. sp. (Nematoda: Rhabditidae): A Facultatively Pathogenic Nematode from Chongming Island, China.

A new species, Oscheius microvilli n. sp., was found on Chongming Island (Shanghai, China). The new species is morphologically similar to the type strain of Oscheius myriophilus, but can be distinguished from it and other species of Oscheius on the basis of unique morphological characteristics of the bursa as well as male papillae. In this new species, the male bursal papillar formula is 2, 1, 3, 3 with everted tips in the first, fifth, and seventh pairs. The bursal rim is jagged, joins together anterior to the spicules, and is partially extended and decorated with microvilli. The spicules are incompletely separated, and the tail does not extend beyond the bursa. Phylogenetic trees of 18S rDNA and internal transcribed spacer indicate that the new species belongs to the insectivora group of the genus Oscheius; it is most closely related to O. myriophilus, and the two species can be distinguished on the basis of their different body length, morphological features of the bursa, and molecular data. The new species is facultatively associated with a bacterial strain of Serratia. The LC50 of this novel nematode against Galleria mellonella was 69.1 dauer juveniles per milliliter after 48 hr of infection.